Studies of immunoglobulin (Ig) synthesis and secretion will be performed on a group of human lymphoblastoid lines in long-term culture, and on human blood lymphocytes by an in vitro culture system. The lymphoblastoid lines will be examined with respect to their kinetics of synthesis and secretion, their surface Ig, cell cycle characteristics, DNA synthesis, and Ig H chains produced to determine a useful classification correlated with in vivo lymphocytes. Blood lymphocytes from immunodeficient persons will be examined in vitro and compared to normal lymphocytes for Ig secretion, synthesis, and surface expression. BIBLIOGRAPHIC REFERENCES: Genetic control of gammaglobulins. S.D. Litwin. In Combined Immunodeficiency Disease and Adenosine Deaminase Deficiency, Proceedings of Birth Defects Institute Symposium on Combined Immunodeficiency. Academic Press, p. 13, 1975. Ankylosing spondylitis and HL-A. A genetic disease plus? M. Lockshin, M. Fotino, W. Gough and S.D. Litwin, Amer. J. Med. 58:695, 1975.